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From Bruce A Johnson <johns...@umbc.edu>
Subject Re: [math] Convolution
Date Thu, 23 Aug 2012 12:52:46 GMT

On Aug 23, 2012, at 8:31 AM, Clemens Novak wrote:

> On 2012-08-20 19:25, Luc Maisonobe wrote:
>> Le 20/08/2012 17:00, Clemens Novak a écrit :
>>> Dear all,
>>
>> Hi Clemens,
>>
>>>
>>> I would like to work on some signal processing functions (as indicated
>>> on the wiki WishList) and started with the convolution of 2 sequences
>>> (represented as RealVector). I have completed a first working version
>>> (some error checking code, formatting, unit tests etc are missing); I am
>>> unsure of how to continue: Is the next step to create a new Jira ticket
>>> and upload my final code there (for further discussion/review/...)?
>>
>> Yes, you can do that.
>>
>>>
>>> Thanks for your help & kind regards - Clemens
>>
>> Thanks for your interest and contribution.
>>
>> Luc
>>
>>>
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>>
>>
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>
> Dear all,
>
> besides the ongoing discussions in MATH-851, I would like to discuss some extensions
of this library in the area of discrete-time signal processing:
>
> (1) convolution of 1D and 2D sequences based on (i) straightforward calculation of the
convolution sum and (ii) using the FFT.
>
> (2) filter functions for 1D sequences, i.e. y[n] = \sum_{l=0}^{L-1} b_l x[n-l] - \sum_{m=1}^{M-1}
a_m y[n-m]
>
> (3) window functions (such as raised cosine, blackmann...) used in conjunction with FFTs
>
> (4) possibly some basic filter design (such as window method, Parks-McClellan algorithm...)
>
> However, first I want to ensure that you think these topics belong in Commons math -
I have been reading the intro (... is a library of lightweight, self-contained mathematics
and statistics components addressing the most common problems...) and I am not perfectly sure
whether these topics really fit here?
>
> In MATH-851 we shortly touched whether using RealVector or a simple double array is better.
What's your opinion here? The double array might be better in terms of performance; when based
on RealVector, however, more basic functionality would be provided out of the box. Has anyone
made a performance comparison between arrays and RealVector in order to have some guidelines
here?
>
> Kind regards - Clemens
>

I use Commons Math extensively in signal processing applications so I, for one, would love
to see more features in this area.

cheers,

Bruce

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